SPERM FILTRATES AND DIALYZATES. 329 



ance or in shape yet may be so influenced that after transfer to 

 sea-water they fail to develop normally if inseminated with fresh 

 sperm. Such was found to be the case in eighteen experiments 

 in which ova were exposed to the action of a number of nitrates 

 and subsequently inseminated in sea-water. Although the sperm 

 were active in the filtrates, few membranes formed and these 

 were abnormal in that they were irregular and but slightly 

 raised from the surface of the egg. Subsequent divisions were 

 irregular; development was slow and abnormal ; and the majority 

 of ova cytolyzed later. Gastrulae formed in a few, but these 

 lacked an enteron, and plutei were irregular in shape with 

 thickened areas not normally present. These resembled plutei 

 obtained when ova are inseminated with a large excess of sperm 

 when polyspermy is known to occur. 



A correlation between the reversibility of changes in ova 

 produced by abnormal constituents in sea-water and the duration 

 of their exposure to these substances has been recorded by Loeb 

 (1915) for butyric acid and hypertonic sea-water; by Lillie 

 (1921) for copper; and by Clowes and Smith (1923 and 1924) 

 for hydrogen ions. In some instances the change is of such a 

 nature that it acts as a block to the entrance of sperm; in others 

 it permits polyspermy. Just (1923) found that eggs of Rchi- 

 narachnius fertilized in blood, though they fail to develop, 

 nevertheless take in sperm. 



As stated by Clowes (1924) "it is difficult to distinguish 

 polyspermic from abnormally dividing eggs without cytological 

 examination." Such a study of ova of Arbacia inseminated in 

 the sperm filtrates reveals that polyspermy occurred in many of 

 the ova. 



The interference with the fertilization process may be due in 

 part to injury to the sperm caused by the sperm filtrate. How- 

 ever, examinations of suspensions of sperm in filtrates reveal 

 that the sperm remain active in such suspensions for hours. 

 Furthermore if such sperm are used for insemination of ova in 

 sea-water, they will effect normal fertilization and development. 

 The results tabulated below indicate that the sperm are not 

 injured by an exposure of one hour either to sea-water or to a 

 sperm filtrate in the concentrations employed; but that ova 



